Tone generation system



April 9, 1963 M. E. ANDERSON 3,084,583

TONE GENERATION SYSTEM Filed Oct. 20, 1958 2 Sheets-Sheet 1 LOIJPL/NG TRANSFORMER 1 j; J

x AMPLIFIER I, I a v I J in Id u u u u u u u u M u I vs 1s 35 20 IL I I V LL a 2222* Mart Ln E Anderson April 9, 1963 M. E- ANDERSON TONE GENERATION SYSTEM 2 Sheets-Sheet 2 Filed Oct he afar Marvin 5. Anderson United States Patent 3,084,583 TONE GENERATION SYSTEM Marvin E. Anderson, Chicago, Ill, assignor, by mesne assignments, to Everett Piano Company, South Haven, Mich, a corporation of Delaware Filed Oct. 20, 1958, Ser. No. 768,131 3 Claims. (Cl. S i -1.16)

This invention relates generally to an improved electronic piano, and more specifically to an improved simplified tone generation system incorporated therein.

Although the principles of the present invention may be included in various musical instruments, a particularly useful application is made in an electronic piano of the lightweight type which can be sold at a somewhat lower price .than conventional pianos.

Broadly speaking, electronic pianos are old and known in the art. These pianos have had various faults or difficulties, one of which is an excessive degree of complexity, particularly in the electrical details employed in the generation of the musical tones.

Accordingly, it is a principal object of the instant invention to provide a simplified tone generation system for an electronic piano.

It is the further object of the present invention to provide a simplified tone generation system incorporating novel simplified means for providing a magnetic field adjacent to portions of the various strings of the piano.

A still further object of the present invention is to provide a tone generation system of the type wherein the strings are electrically connected together, and wherein novel means are provided for effecting such connection together of the tuned strings.

Many other advantages, features and additional objects of the present invention will become manifest to those versed in the art upon making reference to the detailed description and the accompanying sheets of drawings in which preferred structural embodiments incorporating the principles of the present invention are shown by way of illustrative example.

On the drawings:

FIGURE 1 is an elevational view of a piano equipped with a tone generation system provided in accordance with the principles of the present invention, portions of the illustrated embodiment of the invention being broken away and other structural portions of a known environmental nature being shown largely diagrammatically to simplify the illustration;

FIGURE 2 is a diagrammatic view of the electrical circuit employed in .the tone generation assembly shown in FIGURE 1;

FIGURE 3 is an enlarged plan view, fragmentary in nature, of a field producing portion of FIGURE 2, taken near the right end thereof;

FIGURE 4 is a perspective fragmentary view of a different field-producing portion of FIGURE 2, taken near the left end thereof;

FIGURE 5 is a front elevational view substantially of the fragmentary portion of the structure shown in FIGURE 4;

FIGURE 6 is a slightly modified form of field producing means, generally similar to the embodiment shown in FIGURES 3 and 4;

FIGURE 7 is a fragmentary view of a string frame assembly showing one means for connecting the strings in series;

FIGURE 8 is generally similar to FIGURE 7, but illustrates a second means for connecting the strings in series;

FIGURE 9 is an enlarged perspective view of a clip used in FIGURE 8;

FIGURE 10 illustrates a third way of connecting the strings in series;

FIGURE 11 is an enlarged perspective view of a clip used in FIGURE 10;

FIGURE 12 illustrates a fourth method of connecting the strings in series;

FIGURE 13 is an enlarged perspective view of a clip used in FIGURE 12; and

FIGURE 14 illustrates a fifth means for connecting the strings in series.

As shown on the drawings:

The principles of the present invention are particularly useful when embodied in an electrical musical instrument or piano such as illustrated in FIGURE 1, generally indicated by the numeral 10. The piano 10 includes a cabinet 11 supporting a string frame assembly 12 and an action assembly diagrammatically illustrated by the hammer 13 for exciting a string 14 of the string frame assembly 12. An electrical field producing member 15, described in greater detail later herein, is also included in the string frame assembly 12, and communicates electromechanically with .the strings for converting the vibrations thereof into electrical signals. The strings 14 communicate electrically with an electronic amplifier 16 which drives a speaker 17, both supported by the case 11. Conventional structure may be utilized for each of the components not described in detail in the instant specification, such as the amplifier 16, the speaker 17, the cabinet 11 and the hammer 13.

Referring now to the circuit diagram of FIGURE 2, the instant tone generation system includes a plurality of the strings 14 which are each secured at one end to a hitch pin or string-supporting pin 20 and at the other end to a tuning pin or string-supporting pins 21 as shown in FIGURE 1. The frame 12 has a hearing edge or bridge 22 adjacent to the tuning pins 21, and has a second bearing edge or bridge 23 adjacent to the hitch pins 20. The bridges 22 and 23 are spaced apart so as to jointly define the speaking portion or vibrating portion of each of the strings 14.

The number of strings 14 corresponds exactly to the number of notes in the series which the instrument 10 provides. Thus, one feature of the instant invention is that only one string is provided per musical note.

The circuit illustrated in FIGURE 2 has 88 strings representing the quantity required for a full scale piano having a standard keyboard. Each of the tuning pins 21 is so adjusted that the strings 14 are tuned to provide an equal tempered chromatic scale, such as one with a standard pitch for each string. Thus there is a series of hitch pins 20 which are spaced from each other and which are supported by the string frame of the string frame assembly 12. In this embodiment, each of the hitch pins 20 is electrically isolated from each other, insofar as its support is concerned.

Thus also there is provided a series of the tuning pins 21 each of which is supported by the frame of the frame assembly 12 in spaced relation to each other, and each of which is also electrically insulated from the other pins, insofar as the support is concerned. Since the string frame of the string frame assembly 12 is substantially fiat, the various vibratory strings 14 are each supported and tensioned between a hitch pin 20 and a tuning pin 21, and disposed by them substantially in a plane.

While the means 15 has been broadly termed a field producing member, it is more accurately a series of means for providing magnetic fields about a portion of each of the strings 14. As shown in FIGURE 2, the field producing member 15 may be subdivided into several components and may be provided in various angles and lengths.

Referring now to FIGURES 3-5, the magnetic field means in this embodiment is shown to include an elongated non-rnagnetic base 3d, which in this embodiment comprises wood. As best seen in FIGURE 1, the base 3t) is supported in fixed relation to the string (frame assembly '12 by the string frame itself, and in a position adjacent to a group of the strings 14, in parallel relation to the plane in which the strings 14 lie. To the one surface of the base 30 which is adjacent to the strings 14, there is attached a series or group of flat wafer-like magnetic elements 31, 32, which comprise permanent magnets. The magnetic elements 31, 32 are fixedly secured in flatwise relation against the base 30 and are disposed in spaced relation to each other. it will thus be seen that edges of adjacent elements which confront each other jointly define a gap within which a string 14 is disposed as seen in FIGURES 3 and 5. The magnetic elements 31, 32 have such magnetic polarity that the confronting edges which define the gap also have the magnetic poles.

It will be noted that along one polar edge, there is but one polarity so that each of a pair of adjacent spaced edges has continual but mutually opposite magnetic polarities, whereby a single polarity is provided at each side of the gap without there being a null point along the length of the gap.

Where the magnetic elements 31, 32 are made up from premagnetized strips of a permanent magnet, such strips being transversely magnetized, they may be cut to different lengths, as illustrated by the diiference in lengths between the elements 31 and 32., so as to thereby selec'tably determine the amount of flux which is present around a particular string. Therefore, it is apparent that the magnetic fiux will be somewhat greater between the elements 31 and 32 than it will be between a pair of the elements 31, 31. This difference is utilized to obtain a uniform well-balanced ensemble of strings.

If desired, the base 30 may be undercut as at 30a, the undercut 30a serving as an extension of the gap between two of the magnetic elements. The undercut serves two functions. First it acts as a gage for the alignment of individual elements 31, 32, and secondly, it provides clearance for string vibration.

It is to be understood however, that the slots 30a may be omitted as shown in FIGURE 5, and that the elements 31 may be of the same length as shown in FIGURE 3.

As shown in FIGURE 2, there is a series of means provided at each of the ends of the strings 14 whereby all of the strings are connected together in a single series circuit. This is illustrated in FIGURE 2 by the wires 33 and the wires 34. Further, means is provided for coupling the ends of the circuit to the audio amplifier 16, which in this embodiment includes a wire 35, a wire 36, and a coupling transformer 37. When one of the polyphonically tuned strings 14 is excited into vibration by being struck by the hammer 13, that portion of the string 14 which is disposed within the magnetic field between the permanently magnetic elements 31, cuts across the magnetic lines of force in the gap to induce a current in the wire. I have found that where a single wire is used per note, and particularly when miniaturized or relatively short low tensioned strings are employed in the electronic piano, all of the strings may be connected in a single series. The total electrical resistance of all the strings, even though made of piano wire, does not adversely affect the operation of the piano. I have also found that when the strings are connected as shown, the various electrical signals which may exist simultaneously in the circuit when the piano is played do not interfere constructively or destructively with each other, other than to the extent which simultaneously existing sounds combine. Thus the composite of all of these signals generated by and within the strings is conducted by the wires 35 and 36 to the step-up coupling transformer 37 which is 4 connected to the amplifier 16 which strengthens the sig nal so that they can be converted to sound by the speaker 17.

It will be noted that the means for producing the magnetic field can be manufactured employing only cut-off equipment, since cement may be employed to secure the elements 31 to the base 30.

Referring now to FIGURE 6, there is shown another embodiment of the means for producing a series of magnetic fields about a series of the strings. This means also includes an elongated non-magnetic base 40 to which is attached a'group of flat wafer-like magnetic elements 41, each of which is fixedly secured as by cementing in flatwise relation against the base 40 in spaced relation to each other. A pair of magnetic support members 42, 42 is secured to the ends of the non-magnetic base 44 Each of the members '42 communicates magnetically with one of the magnetic elements 41 and is adapted to be sup ported by the string frame of the string frame assembly 12 in fixed relation adjacent to a group of the strings 14;,- parallel to the plane in which the strings are disposed, There is also provided a single permanent magnet 43 which is longitudinally magnetized so that its poles com municate magnetically with each of the magnetic mem* bers 42 remotely from the magnetic elements 4 1. In this embodiment, the screws 44 serve not only to hold the members 42 to the base 40, but also to serve to clamp the permanent magnet 43 therebetween. Of course, the magnetic force of the permanent magnet 43 also serves to assist in holding the magnet 43 in place.

The magnetic path from the magnet 43 extends through the members 42 and thence to the magnetic elements 41; Each of the air gaps between the magnetic elements 41- is a magnetic gap in the circuit which individually receives one of the strings 14, and which collectively have substantially the same effect as a single gap in the circuit having a width equal to the sum of the separate gaps. I have found that this form of construct-ion is advantageous in that a single strong magnet is employed in an extremely simple structure to provide a whole series of magnetic gaps. Each of the magnetic elements thus has an edge which defines a side Oif a gap, and which edge has a magnetic polarity that is continuous along the length of the gap without there being a null point in the gap. Thus a given pair of spaced polar edges have continual but op posite magnetic polarities respectively. Once this embodiment of means for producing a magnetic field is installed in the string frame assembly 12, its operation is identical to that already described above.

Referring again to FIGURE 2, it can be seen that an 88-note tone generation system of this type requires 176 connections of the type made by the wires 3336 to place them electrically in series. Apart from the labor factor, there are other considerations which must be given due regard in effecting the connection between the strings. Among these are electrical characteristics, economy, corrosion eifects, serviceability, and appearance. However, perhaps the most important is that the connections between the piano wires must be secure so that vibration will not loosen or cause intermittent or electrically noisy contact. Since the resistance of all of the strings in series and the voltage produced by them are both low, any further resistance added in series with the strings by poor or resistive connections reduce sensitivity and also reduces the signal-to-noise ratio when a coupling transformer is employed. Obviously, if the transformer were omitted, resistive connections would not be critical to the performance of the system, the series of connected strings then being in communication directly with an am- .plifier grid.

One of the disadvantage of wires soldered to the strings as jumpers, is that a considerable amount of labor is needed and some skill is required. Moreover, if cold soldered joints result from inadequate heat or the like,

sensitivity of the system is reduced due to the added resistance of the series connection.

Accordingly, there is also presented here the teaching of several methods of producing efiective connections.

Referring first to FIGURE 7, it can be seen that each of the series of means connecting all of the strings together in a single circuit can comprise a series of bridge elements 45 disposed at opposite ends of the strings to jointly define the speaking length thereof. The elements 45 comprise conductive inserts which are supported by the bridges 22, 23, the bridges 22, 23 being insulative material. Thus the bridge elements 45 are supported by the string frame in positive electrical engagement with each of a pair of adjacent strings 14.

Referring now to FIGURES -8, l0, l2, and 14, the string frame assembly 12 may also employ a bridge 22 which is provided with a common insulative bridge element 46 such as of hard plastic.

The form shown in FIGURE 14 further includes a series of electrical terminals 47 insulatedly carried by the frame 12 and disposed adjacent to each of the tuning pins 21 and hitch pins 20. The strings 14 in this embodiment are provided with free ends 14a which extend from each of the tuning pins 21 and which are mechanically and electrically secured to the terminal 47. Thus this embodiment also provides means for connecting the strings together which means is supported by the string frame in positive electrical engagement with each of a pair of adjacent strings. This form is also disadvantageous as compared to other forms in that a considerable amount of labor is needed in the installation.

Referring now to FIGURES and 11, there is shown a preferred form for making the connection between various pairs of strings so as to effect a suitable circuit. In FIGURE 11, there is shown an electrically conductive clip 48 which has abroad lower resistance central region and which is provided with a pair of arcuately formed end portions 49, 49, the end portions 49 each having an outwardly or concavely directed surface. As best seen in FIGURE 10, the end portions 49 are received by the string frame 12 in the holes provided therein for the tuning or hitch pins. Thus the clips engage and electrically connect adjacent pairs of hitch and tuning pins, and thus are supported by the string frame in positive electrical engagement with each of a pair of adjacent strings. The clips 48 are inserted in the string frame before the hitch pins are inserted, and then the pins are driven in in a con ventional way, thereby assuring an extremely tight and close fit.

Referring now to FIGURES 8 and 9, there is shown a slightly different form of electrically conductive clip 50, which likewise has arcuately formed end portions 51 adapted to engage and electrically connect adjacent pairs of hitch and tuning pins as shown in FIGURE 8. The material from which the clip 50 is made is an electrically conductive spring material. The end portions 51 are integral with the clip 50' and comprise resilient semicylindrically formed end portions, which concentrically receive a pair of pins 20, 20 or 21, 21, and electrically connect the same together. This form of clip is particularly advantageous for field service since it can be readily attached to or removed from an assembled piano. It is further advantageous in that it provides a relatively large area of contact surface between the clip 50 and the respective pins 20, 21.

Referring now to FIGURES l2 and 13, there is shown a still further form of electrically conductive clip 52. The clip 52 is provided with a pair of integral longitudinally extending resilient fingers 53, 53, each of which is provided with a concavely formed end portion 530. As best seen in FIGURE 12, the spring clip 52 may be disposed between a pair of pins 21 so that the arcuately formed end portions resiliently engage and electrically connect the adjacent pins. The edges formed at the arcuate end portions are relatively sharp, and since they are disposed to engage the pin 21, they tend to bite in and to hold or wedge in a positive manner.

It is thus apparent that the instant tone generation system is extremely simple and foolproof. The position of the string laterally within the magnetic gap is not critical assuming of course that the string does not touch the magnetic elements during vibration. The transverse position of the string in the magnetic gap is not critical pro vided that the string is wholly within the gap. Adjustment for sensitivity of pickup of individual strings or groups may be made by disposing the string partly out of the gap.

Although various minor modifications might be suggested by those versed in the art, it should 'be understood that I wish to embody within the scope of the patent warranted hereon all such embodiments as reasonably and properly come within the scope of my contribution to the art.

I claim as my invention:

1. In a tone generation system for an electronic piano having a string frame, a series of spaced hitch pins and a series of spaced tuning pins, each pin being supported by the frame in electrical isolation from each other, a series of polyphonically tuned vibratory strings corresponding in number to the number of notes in the piano and each tensionably supported between one of the hitch pins and one of the tuning pins in a plane, means connecting said strings together in a conducting circuit, and means for coupling the ends of the circuit to an amplifier, the improvement in combination therewith comprising: an elongated non-magnetic base supported by the string frame adjacent to a group of the strings and disposed parallel to said plane; and a group of flat wafer-like permanent magnets fixedly secured in flatwise relation against said non-magnetic base and lying in the plane of the strings in spaced relation to each other, and polar edges of adjacent magnets facing directly toward each other and jointly defining an air gap therebetween, the poles of said magnets being so arranged that each magnet has only one magnetic polarity at said gap.

2. In a tone generation system for an electronic piano having a string frame, a series of spaced hitch pins and a series of spaced tuning pins, each pin being supported by the frame in electrical isolation from each other, a series of polyphonically tuned vibratory strings corresponding in number to the number of notes in the piano and each tensionably supported between one of the hitch pins and one of the tuning pins in a plane, means connecting said strings together in a conducting circuit, and means for coupling the ends of the circuit to an amplifier, the improvement in combination therewith comprising: an elongated nonmagnetic base supported in fixed relation to the string frame and adjacent to a group of the strings in parallel relation to said plane; a group of flat wafer-like elements fixedly secured in flatwise relation directly against said non-magnetic base in spaced relation to each other, the confronting edges of a pair of adjacent elements respectively having continual opposite magnetic polarities and defining an air gap for a string therebetween wherein there is a single magnetic polarity at each side of said gap.

3. In a tone generation system for an electronic instrumenthaving a series of polyphonically tuned vibratory strings disposed in a plane and connected electrically together in a circuit, the improvement comprising: an elongated non-magnetic base disposed adjacent to a group of the strings in parallel relation to said plane; a group of more than two flat wafer-like magnetic elements fixedly secured in flatwise relation directly against said nonmagnetic base in spaced relation to each other, and pairs of adjacent magnetic elements jointly defining an air gap therebetween; a pair of magnetic support members each respectively secured to one end of said non-magnetic base and each communicating magnetically with non-adjacent elements of said group of magnetic elements; and

a permanent magnet having poles communicating magnetically with each of said magnetic support members remotely from said Wafer-like magnetic elements, so that there is a single magnetic polarity induced by said permanent magnet at each side of said gaps.

References Cited in the file of this patent UNITED STATES PATENTS 1,576,545 Powers Mar. 16, 1926 

1. IN A TONE GENERATION SYSTEM FOR AN ELECTRONIC PIANO HAVING A STRING FRAME, A SERIES OF SPACED HITCH PINS AND A SERIES OF SPACED TUNING PINS, EACH PIN BEING SUPPORTED BY THE FRAME IN ELECTRICAL ISOLATION FROM EACH OTHER, A SERIES OF POLYPHONICALLY TUNED VIBRATORY STRINGS CORRESPONDING IN NUMBER TO THE NUMBER OF NOTES IN THE PIANO AND EACH TENSIONABLY SUPPORTED BETWEEN ONE OF THE HITCH PINS AND ONE OF THE TUNING PINS IN A PLANE, MEANS CONNECTING SAID STRINGS TOGETHER IN A CONDUCTING CIRCUIT, AND MEANS FOR COUPLING THE ENDS OF THE CIRCUIT TO AN AMPLIFIER, THE IMPROVEMENT IN COMBINATION THEREWITH COMPRISING: AN ELONGATED NON-MAGNETIC BASE SUPPORTED BY THE STRING FRAME ADJACENT TO A GROUP OF STRINGS AND DISPOSED PARALLEL TO SAID PLANE; AND A GROUP OF FLAT WAFER-LIKE PERMANENT MAGNETS FIXEDLY SECURED IN FLATWISE RELATION AGAINST SAID NON-MAGNETIC BASE AND LYING IN THE PLANE OF THE STRINGS IN SPACED RELATION TO EACH OTHER, AND POLAR EDGES OF ADJACENT MAGNETS FACING DIRECTLY TOWARD EACH OTHER AND JOINTLY DEFINING AN AIR GAP THEREBETWEEN, THE POLES OF SAID MAGNETS BEING SO ARRANGED THAT EACH MAGNET HAS ONLY ONE MAGNETIC POLARITY AT SAID GAP. 